Ti-alloy/Ni-Cr-Mo steel joint bonded with Ta foil insert metal by HIP treatment

摘要

Up to this time, tensil strength of Ti-alloy/steel joint was about 25% (about 300 MPa) as compared with that of Ti-alloy base metal. In this paper, Ti-alloy/Ni-Cr-Mo steel joint was bonded with Ta foil insert metal by Hot Isostatic Press (HIP)treatment. Tensil strength of this joint was about 70% (about 765 MPa) as compared with that of Ti-alloy base metal.The authors examined the cause of such high tensil strength. By means of EPMA and X-ray diffraction analysis, the microstructures of Ti-alloy/Ta foil/Ni-Cr-Mo steel joint bonded were investigated. The main result obtained are as follows: (1) Ta foilinsert metal prevent the diffusion of Fe and Ni from Ni-Cr-Mo steel to Ti-alloy and the diffusion of Ti from Ti-alloy to Ni-Cr-Mo steel. (2) Ta-carbides (TaC, Ta{sub}2C) are formed at the interface between to Ta foil and Ni-Cr-Mo steel. (3) Ta-carbidesprevent the formation of brittle Fe-Ti intermetallic compound.